PresentationsCopyright (c) 2017 Utah State University All rights reserved.http://digitalcommons.usu.edu/mp_presentations
Recent documents in Presentationsen-usSun, 22 Oct 2017 01:53:48 PDT3600An Enhanced Operational Definition of Dielectric Breakdown for DC Voltage Step-up Testshttp://digitalcommons.usu.edu/mp_presentations/149
http://digitalcommons.usu.edu/mp_presentations/149Fri, 20 Oct 2017 09:49:16 PDTAllen Andersen et al.Electron Yield Measurements of Vertically Aligned Multi-Walled Carbon Nanotubeshttp://digitalcommons.usu.edu/mp_presentations/148
http://digitalcommons.usu.edu/mp_presentations/148Fri, 20 Oct 2017 09:49:13 PDTBrian Wood et al.Pulsed Electro-Acoustic Measurements of Charging and Relaxation in Low Density Polyethylenehttp://digitalcommons.usu.edu/mp_presentations/147
http://digitalcommons.usu.edu/mp_presentations/147Fri, 20 Oct 2017 09:49:09 PDTZachary Gibson et al.Measuring and Modeling the Conductivity of Highly Insulating Materialshttp://digitalcommons.usu.edu/mp_presentations/146
http://digitalcommons.usu.edu/mp_presentations/146Fri, 20 Oct 2017 09:49:06 PDTDavid King et al.Development of Updated Spacecraft Materials Database for Mitigation of Charging Riskhttp://digitalcommons.usu.edu/mp_presentations/145
http://digitalcommons.usu.edu/mp_presentations/145Fri, 20 Oct 2017 09:49:02 PDTPhillip Lundgreen et al.Electron Yield of Challenging Materials: Low Density Polyethylene and Carbon-composite Nanodielectricshttp://digitalcommons.usu.edu/mp_presentations/144
http://digitalcommons.usu.edu/mp_presentations/144Fri, 20 Oct 2017 09:48:58 PDT
The electron yield—the ratio of the number of emitted electrons to incident electrons—is a key material property that characterizes how materials will charge due to exposure to electron fluxes. The USU Materials Physics Group has developed expertise in measuring this for a wide array of conductors, semiconductors and insulators, including many challenging materials. The basic definitions associated with electron yield and how they are measured will be discussed. We will highlight many critical applications investigated at USU, particularly those associated with spacecraft charging as materials interact with space plasma environments. Electron irradiation experiments conducted to investigate the electron transport, charging, discharging, and emission properties of two challenging and technologically useful materials are discussed. The first is the most structurally simple polymeric material, low density polyethylene (LDPE). The electron yield of this ubiquitous thermoplastic is influenced by the material’s very low conductivity and high negative electron affinity. Similar experiments were performed on an epoxy/carbon-fiber composite material used in extreme applications to understand how the results are influenced by the nanoscale structure of the conducting carbon fibers embedded in the dielectric epoxy matrix.
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Matthew Robertson et al.Effects of Temperature and Radiation Dose on Radiation Induced Conductivityhttp://digitalcommons.usu.edu/mp_presentations/143
http://digitalcommons.usu.edu/mp_presentations/143Fri, 20 Oct 2017 09:48:55 PDT
Radiation induced conductivity (RIC) is an important conduction mechanism in highly disordered insulating materials exposed to ionizing radiation. Measurements of RIC as a function of dose rate and exposure time of polymeric and glassy insulators will be presented. RIC results from excitation of carriers into conduction states by the ionizing radiation. The measurements will be discussed in terms of models for the distribution of localized disordered states. The effects of temperature and radiation damage from ionizing radiation on the density and occupation of trap states, and how this affects RIC, will also be discussed.
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JR DennisonOf Mice and Materials: Payoffs of UNSGC Research Infrastructure Awardshttp://digitalcommons.usu.edu/mp_presentations/142
http://digitalcommons.usu.edu/mp_presentations/142Fri, 20 Oct 2017 09:48:51 PDT
A versatile test facility has been designed and built to study space environments effects on small satellites and system components. Testing for potentially environmental-induced modifications of small satellites is critical to avoid possible deleterious or catastrophic effects over the duration of space mission. This is increasingly more important as small satellite programs have longer mission lifetimes, expand to more harsh environments (such as polar or geosynchronous orbits), make more diverse and sensitive measurements, minimize shielding to reduce mass, and utilize more compact and sensitive electronics (often including untested off-the-shelf components). The vacuum chamber described here is particularly well suited for cost-effective, long-duration tests of modifications due to exposure to simulated space environment conditions for CubeSats, system components, and small scale materials samples of >10 cm X 10 cm. The facility simulates critical environmental components including the neutral gas atmosphere, the FUV/UVMS/NIR solar spectrum, electron plasma fluxes, and temperature. The solar spectrum (-120 nm to 2500 nm) is simulated using an Solar Simulator and Kr resonance lamps at up to four Suns intensity. Low and intermediate electron flood guns and a Sr90 β radiation source provide uniform, stable, electron flux (~ 20 eV to 2.5 MeV) over the CubeSat surface at >5X intensities of the geosynchronous spectrum. Stable temperatures from 100 K to 450 K are possible. An automated data acquisition system periodically monitors and records the environmental conditions, sample photographs, UVMS/NIR reflectivity, IR absorptivity/emissivity, and surface voltage over the CubeSat face and in situ calibration standards during the sample exposure cycle.
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JR Dennison et al.Hemispherical Grid Retarding Field Analyzer Redesign for Secondary Electron Emission Studieshttp://digitalcommons.usu.edu/mp_presentations/141
http://digitalcommons.usu.edu/mp_presentations/141Fri, 20 Oct 2017 09:48:47 PDT
A redesign of the Hemispherical Grid Retarding Field Analyzer is discussed in relationship to multilayer charging models. In order to accurately extend single layer charging models to dynamic multilayer scenarios, precise measurements of electron emission as well as the net surface potential must be made. By learning from the previous design and thinking of future applications, the new instrument will greatly enhance our ability to precisely measure materials undergoing energetic electron bombardment.
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Greg Wilson et al.Satellite Survivability in a Harsh Space Environment: A Materials Perspectivehttp://digitalcommons.usu.edu/mp_presentations/140
http://digitalcommons.usu.edu/mp_presentations/140Fri, 20 Oct 2017 09:48:43 PDTJR DennisonLAM Phase I Review: Charge Storage and Transfer in Thin Film Ceramic Materialshttp://digitalcommons.usu.edu/mp_presentations/139
http://digitalcommons.usu.edu/mp_presentations/139Fri, 20 Oct 2017 09:48:40 PDTJR Dennison